Means for breaking foam in steam boilers and other liquid evaporators



Dec. 29, 1931. s. B. BILBROUGH 1,838247 MEANS FOR BREAKING FOAM IN STEAM BOILERS AND OTHER LIQUID EVAPORATORS Filed April 11, 1930 Patented Dec. 29, 1931 UNITED STATES PATENT OFFICE SYDNEY BROOKS BILBROUGH, 0F JOHANNESIBURG, TRANSVAAL, UNION OF SOUTH AFRICA MEANS FOR BREAKING FOAM IN S'IEAM BOILERS AND OTHER LIQUID EVAPORATORS Application filed April 11, 1930, Serial No. 443,513,

ing not merely annoyance but in most cases such a condition as cannot be tolerated.

Many different kinds of apparatus have been designed to prevent foam going over 4 with the steam, such as baflies, which change the direction of the steam and, by centrifugal action, separate the water from the steam. From experiments I have carried out I have ascertained that foam is entirely broken by M passing it through a tube of smallor narrow bore.

Now while foam will pass baflies and arrangements whlch deflect or alter. the direction of the steam, and even pass through wire netting arranged in several layers without being in any way broken, 1f the foam is passed through a small or narrow tube, it is broken and separated into liquid and vapour. This remarkable phenomenon is probably due to some kind of surface action or vortex 30 movement between the tube and films of froth, and this action interferes with the capillary attraction or the surface tension of the bubbles and so renders them unstable during their passage along the tube. This is F" of the highest importance in-practice.

Steam boilers and the like in which impure water is used for generating steam frequently foam very badly, depending on the nature of the impurities, and when the steam is superheated and used in engines or turbines it is a great disadvantage for any foam to pass over with the steam, as it carries with it the impurities contained in the boiling water, and pure steam is not delivered to the steam engines or turbines.

The discovery that foam will not pass through a. tube of small bore is utilized by me in designing my improved foam breaker which effectively and easily destroys the foam, returns the impure water back to the and in Union of South Africa September 4, 1929.

water in the boiler drum, and allows steam alone to pass out to the steam engines or turbines.

In the accompanying drawings I illustrate a practical embodiment of the invention arranged within a steam boiler drum,sufficient of the latter being shown to illustrate the invention arranged in operative position therein. In the drawings,

Fig. 1 is a sectional elevation of the boiler drum with the foam breaker placed in a convenient position at one end thereof.

Fig. 2 is a part-sectional plan of the foam breaker detached, the plane of section being indicated by the dotted line a:n; in Fig. 1.

Fig. 3 is an end elevation of the foam brepker with the steam outlet pipe omitted, anc

Fig. 4; is an end elevation of the foam breaker, as seen from the opposite end to Fig. 3.

The boiler drum in Fig. 1 of the drawings is denoted by the numeral 1, and 2 indicates the water level therein.

In the form of the device or apparatus constructed as illustrated there is employed a hollow cylinder or piece of pipe 3, of suitable diameter and length, which forms a casing or housing for a plurality of tubes 4 of suitable small b0resay flve-eighths of an inch diameter. These tubes et are of a suitable lengthsay one-half of the length of the casing 3-and they extend from one end of the casing 3 in a forward direction. The other end of the casing 3 is shown provided with a flange 5 for bolting or otherwise fixing it to the flanged inner extremity of the steam exit pipe 6.

The space 7 in the casing 3, in front of the inner ends of the tubes t, forms a chamher in which the separated water and steam is received after leaving the inner ends of the tubes 4:. 8 is a downwardly extending portion of the casing 3 of the device, which is constructed in its upper portion with an inclined surface 9. The lower portion 10 is shown of rectangular shape in cross-section and extending downflfor some distance into the water in the boiler drum 1. It is provided on the rear side and extending to the bottom with an opening 11. As shown, the

cross-sectional area of the passage provided by the portion 10, and also of the opening 11, are at least equal to, but preferably greater than the aggregate cross-sectional area of the passages provided through and between the foam breaking tubes 4.

12 are two splash plates'fixed in the casing 3, between the inner ends of the tubes 4 and the steam outlet. These plates operate to prevent anyof the water or liquid being projected from the inner ends of the tubes 4 to the steam outlet. If the steam outlet be arranged to communicate with the top of the casing 3 then the splash plates 12 could be dispensed with.

p In the operation of this form of the device or apparatus, the steam passes through the tubes 4, and any foam associatedwith it is thereby broken and separated into liquid and vapour, which pass from the tubes 4 into the separating chamber 7, the liquid portion gravitating by way of the downwardly extending portion 8 of the casing into the water in the boiler drum 1, and the steam passing out through the steam exit pipe to the steam mains. 7

Although I illustrate the apparatus arrangedin a boiler drum, it will be evident that it could be arrangedin any suitable position outside the drum and the steam be led to the receiving ends of the tubes 4 and from to protect by Letters Patent is 1. Means for breaking foam including a device which provides a plurality of narrow straight passages through which the steam is caused-to pass and in which the foam is broken, a chamber with which the outlet ends of the passages communicate, an outlet from said chamber for the steam, and an outlet from said chamber for the separated water having a cross-sectional area equal to or greater than the aggregate cross-sectional area of the foam breaking passages, as set forth.

2; .Means for breaking foam including a plurality of straight tubes of small bore through which the steam is caused to pass and in which the foam 1s broken, a chamber with which the outlet ends of the tubes com- .municate,,ran outlet from said chamber for the steam, andan outlet from said chamber fortheseparated water having a cross-sec- .tional area equal to or greater than the aggregate cross-sectional area of the foam breaking tubes, as set forth.

3. Means for breaking foam including a casing, a plurality of straight tubes of small bore through and between which the steam is caused to pass and in which the foam is broken, which tubes are supported by said casing and open thereinto, an outlet for the steam in the upper portion of the casing, and an outlet for the separated liquid in the lower portion of the casing, said outlet having a cross-sectional area equal to or greater than the aggregate cross-sectional area of the foam breaking tubes, as set forth.

4. Means for breaking foam including a casing, a plurality of straight tubes of small bore through which the steam is caused to pass and in which the foam is broken, which tubes are supported by said casing and open thereinto, an outlet for the steam in the upper portion of the casing, an outlet for the separated liquid in the lower portion of the casing, said outlet having a crosssectional area equal to or greater than the aggregate cross-sectional area of the foam breaking tubes, and means in the form of splash plates arranged in the casing between the inner ends of the tubes and the steam outlet, as set forth.

5. Means for breaking foam in steam boilers including a casing, a plurality of straight tubes of small bore in the passages through and between which the steam is caused to pass, and in which passages the foam is broken, which tubes are supported by said casing and open thereinto, an outlet for the steam in the upper portion of the casing, an outlet for the separated liquid in the lower portion of the casing, said outlet having a cross-sectional area equal to or greater than the aggregate cross-sectional area of the foam breaking passages, and means for leading the liquid from the liquid outlet in the bottom of the casing to the water in the boiler, as set forth. 6. Means for breaking foam in steam boilers, including the combination with a boiler drum of a casing arranged in said boiler drum, and a plurality of straight tubes of small bore, open at both ends and filling said casing for a portion of its length, the said tubes providing passages through and between them for the steam to pass into the casing, and serving to break the foam, said casing having an outlet for the steam and a downwardly depending lower portion extendinginto the water in the boiler drum, for leading the separated water into the water in the boiler drum, said lower portion having a cross-sectional area equal to or greater than the aggregate cross-sectional area of the foam breaking passages, as set forth.

In testimony whereof I have signed my name to this specification.

SYDNEY BROOKS BILBROUGH. 

